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"""
pint.facets.nonmultiplicative.definitions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:copyright: 2022 by Pint Authors, see AUTHORS for more details.
:license: BSD, see LICENSE for more details.
"""
from __future__ import annotations
from dataclasses import dataclass
from ..._typing import Magnitude
from ...compat import HAS_NUMPY, exp, log
from ..plain import ScaleConverter
@dataclass(frozen=True)
class OffsetConverter(ScaleConverter):
"""An affine transformation."""
offset: float
@property
def is_multiplicative(self):
return self.offset == 0
def to_reference(self, value: Magnitude, inplace: bool = False) -> Magnitude:
if inplace:
value *= self.scale
value += self.offset
else:
value = value * self.scale + self.offset
return value
def from_reference(self, value: Magnitude, inplace: bool = False) -> Magnitude:
if inplace:
value -= self.offset
value /= self.scale
else:
value = (value - self.offset) / self.scale
return value
@classmethod
def preprocess_kwargs(cls, **kwargs):
if "offset" in kwargs and kwargs["offset"] == 0:
return {"scale": kwargs["scale"]}
return None
@dataclass(frozen=True)
class LogarithmicConverter(ScaleConverter):
"""Converts between linear units and logarithmic units, such as dB, octave, neper or pH.
Q_log = logfactor * log( Q_lin / scale ) / log(log_base)
Parameters
----------
scale : float
unit of reference at denominator for logarithmic unit conversion
logbase : float
plain of logarithm used in the logarithmic unit conversion
logfactor : float
factor multiplied to logarithm for unit conversion
inplace : bool
controls if computation is done in place
"""
# TODO: Can I use PintScalar here?
logbase: float
logfactor: float
@property
def is_multiplicative(self):
return False
@property
def is_logarithmic(self):
return True
def from_reference(self, value: Magnitude, inplace: bool = False) -> Magnitude:
"""Converts value from the reference unit to the logarithmic unit
dBm <------ mW
y dBm = 10 log10( x / 1mW )
"""
if inplace:
value /= self.scale
if HAS_NUMPY:
log(value, value)
else:
value = log(value)
value *= self.logfactor / log(self.logbase)
else:
value = self.logfactor * log(value / self.scale) / log(self.logbase)
return value
def to_reference(self, value: Magnitude, inplace: bool = False) -> Magnitude:
"""Converts value to the reference unit from the logarithmic unit
dBm ------> mW
y dBm = 10 log10( x / 1mW )
"""
if inplace:
value /= self.logfactor
value *= log(self.logbase)
if HAS_NUMPY:
exp(value, value)
else:
value = exp(value)
value *= self.scale
else:
value = self.scale * exp(log(self.logbase) * (value / self.logfactor))
return value
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